1. Field of the Invention
The present invention relates to a lubrication structure to a camshaft of a valve mechanism of an internal combustion engine and to a lubricating oil supplying structure for a valve apparatus of an internal combustion engine.
2. Description of Background Art
In a lubrication path of lubricating oil for camshafts wherein intake and exhaust cams for opening and closing intake and exhaust valves of a valve mechanism of an internal combustion engine are provided, a main lubricating oil passage is provided in a cylinder head. The main lubricating oil passage extends in parallel to and is positioned between an intake camshaft and an exhaust camshaft. Lubricating oil is supplied from an oil pump to the main lubricating oil passage. Since the main lubricating oil passage is disposed between the intake camshaft and the exhaust camshaft, a plug hole in which an ignition plug is fitted is formed for each cylinder between the intake camshaft and the exhaust camshaft and crosses with and divides the main lubricating oil passage. Therefore, an annular tubular member is inserted in the plug hole and mounted liquid-tight in the plug hole above and below the main lubricating oil passage to form a bypassing oil passage on an outer periphery of the plug tube such that the main lubricating oil passage is connected to the oil passage.
Further, a guide passage is formed on the downstream side of the main lubricating oil passage through a communication passage and an extension passage and extends in an upward and downward direction toward a bearing region positioned at an axial end of each camshaft so as to lubricate the bearing region. In addition, although at least a plurality of bearing regions for each camshaft are provided at different locations, if it is tried to provide an oil passage such as a communication passage, an extension passage or a guide passage formed independently of each other at each bearing region, then it is necessary to consider the arrangement space for the oil passages or the workability of a cylinder head. Therefore, there is the possibility that this may cause an increase in the size of the cylinder head. Thus, it is desired to provide a cam bearing lubrication structure for an internal combustion engine that is easy to service while oil passages to different locations are reduced in length. See, for example, Japanese Patent No. 3198689.
As a lubricating oil supplying structure for a valve apparatus of an internal combustion engine, a lubricating oil supplying structure is available wherein a lubricating oil path along which oil is discharged toward a contact region between an adjust bolt and a valve stem from among sliding regions of a rocker arm is provided in the rocker arm. Conventionally, one of such lubricating oil supplying structures for a valve apparatus is disclosed, for example, in Japanese Patent No. 4220415. In the lubricating oil supplying structure for the valve apparatus disclosed in Japanese Patent No. 4220415, a lubrication passage is provided in a rocker arm shaft such that oil is supplied to a sliding face between the rocker arm shaft and a rocker arm from the lubrication passage. The oil supplied from the sliding face is injected from a lubricating oil passage provided in the rocker arm shaft to a contact region between an adjust bolt and a valve stem.
In Japanese Patent No. 4220415, the amount of oil supplied to an ejection port of each rocker arm when oil is branched and shunted to the rocker arm shaft decreases. Further, the lubrication oil to the ejection hole of each rocker arm becomes long. In addition, since part of the oil supplied to the sliding face between the adjust bolt and the valve stem is injected, there is a limit to the assurance of the supply amount of oil. Therefore, where a further fuel supply amount is demanded from an increase in the speed of rotation of an engine, it is necessary to improve the oiling system.
The present invention solves such a subject of the prior art, and it is an object of an embodiment of the present invention to provide a cam bearing lubrication structure wherein the space of an oil passage is prevented from increasing to miniaturize a cylinder head. Thus, miniaturization of an internal combustion engine is achieved while oil passages to bearings for intake and exhaust camshafts are reduced in length. In addition, servicing is facilitated and the fabrication cost is reduced.
In order to attain the object described above, according to an embodiment of the present invention, a cam bearing lubrication structure for an internal combustion engine includes a cylinder head having a cam bearing region on which a camshaft is supported for rotation, a plug hole in which an ignition plug supported on the cylinder head is accommodated such that an end thereof is exposed to a combustion chamber, and a plug tube having a cylindrical shape and fitted liquid-tight at upper and lower end portions thereof in the plug hole to separate the inside of the cylinder head and the plug hole from each other. The cam bearing lubrication structure for the internal combustion engine further includes an outer periphery oil path formed liquid-tight at the upper and lower end portions of the plug tube with respect to the plug hole and bypassing along an outer peripheral face of the plug tube. A main lubricating oil passage extends through the plug hole in the cylinder head and is formed so as to connect to the outer periphery oil path. A guide passage is formed in and through the cam bearing region so as to connect a sliding face of the cam bearing region from the outer periphery oil path and supplying lubricating oil to a sliding face of the cam bearing region and the camshaft.
According to an embodiment of the present invention, an outlet of the guide passage to the cam bearing region is provided on a semicircular face at the plug hole side with respect to the center of rotation of the camshaft.
According to an embodiment of the present invention, the cam bearing region is configured from a plurality of divisional halves. A threaded hole, provided between the camshaft and the plug hole and used for a fastening member which couples the divisional half, is formed such that the guide passage extends therethrough. The threaded hole is sealed by the fastening member.
According to an embodiment of the present invention, the cam bearing region is configured from divisional upper and lower halves with the guide passage being formed by working in such a manner so as to be inclined with respect to a mating plane of the upper and lower halves toward the plug hole.
According to an embodiment of the present invention, the cylinder head has a plurality of camshafts provided thereon sandwiching the plug hole therebetween with a pair of guide passages being formed for each of the cam bearing regions.
According to an embodiment of the present invention, a protuberance is provided at a position below an upper end face of the plug tube and between the position of an inlet of the guide passage in such a manner as to protrude annularly from an outer periphery of the plug tube.
According to an embodiment of the present invention, a holder unit is disposed at an upper end face of the upper end portion of the plug tube so as to closely contact with the upper end face to fix the plug tube from coming off from above with an annular seal member interposed therebetween.
According to an embodiment of the present invention, the cam bearing region is configured from upper and lower halves formed as upper and lower divisional portions, and the holder unit is configured integrally with the upper half.
According to an embodiment of the present invention, the upper and lower end portions of the plug tube are fitted liquid-tight in the plug hole to form the outer periphery oil path. The guide passage is formed from the outer periphery oil path in such a manner so as to connect the cam bearing region. Consequently, oil is directly supplied from the outer periphery oil path to the cam bearing region through the guide passage. Thus, the oil passage to the cam bearing region can be reduced in length, and as a result, it is possible to reduce the size of the cylinder head to achieve miniaturization of the internal combustion engine.
According to an embodiment of the present invention, the outlet of the guide passage from the outer periphery oil path is provided on the semicircular face of the cam bearing region at the plug hole side. Therefore, it is possible to reduce the length of the guide passage to the utmost and reduce the time for oil supply to the cam bearing region after the internal combustion engine is started up.
According to an embodiment of the present invention, the guide passage is formed so as to extend through the threaded hole between the camshaft and the plug hole, and the guide passage is sealed by the fastening member. Therefore, in comparison with an alternative case in which the guide passage is formed bypassing the threaded hole, the guide passage can be connected in the shortest length, and it is possible to reduce the working cost.
According to an embodiment of the present invention, the cam bearing is formed from upper and lower halves, and when the guide passage is formed by working from the bearing formed as the two divisional upper and lower portions, by working the cam bearing region obliquely, the working procedure can be carried out readily.
According to an embodiment of the present invention, the supply of oil to the cam bearing regions at the opposite sides sandwiching the plug hole can be carried out from the outer periphery oil path of the common plug hole. Thus, the oil supply path can be simplified.
According to an embodiment of the present invention, the annular protuberance is provided on the outer periphery of the plug tube at a position above the inlet of the guide passage. Therefore, the flow of oil, which has flowed from below into and flowed upwardly in the outer periphery oil path into the inlet of the guide passage, can be promoted to facilitate the supply of the oil into the guide passage.
According to an embodiment of the present invention, the upper end face of the plug tube, which configures part of the outer periphery oil path, is fixed from coming off from above by the holder unit through the annular seal member. Therefore, the plug tube which is acted upon by hydraulic pressure and is likely to come off can be suppressed with certainty.
According to an embodiment of the present invention, the cam bearing region is configured from the upper and lower halves formed as upward and downward divisional portions. When the holder unit is provided, by forming the holder unit integrally with the upper half of the cam bearing region a reduction in the number of parts can be anticipated. Thus, a reduction in the fabrication cost can be anticipated.
In addition, it is an object of an embodiment of the present invention to provide a lubricating oil supplying structure for a valve apparatus of an internal combustion engine wherein the oil supplying amount is further increased in accordance with an increase in the speed of rotation of the engine.
According to an embodiment of the present invention, a lubricating oil supplying structure for a valve apparatus of an internal combustion engine having a cylinder head which supports camshafts for rotation thereon includes, for each pair of engine valves for intake and exhaust, rocker arms supported at pivotally supporting base portions thereof for rocking motion by rocker arm shafts. The rocker arms are interposed between valve stem axial ends of the engine valves and cam faces of the camshafts to allow contact therebetween. Pressing force from the cam faces acting upon the rocking arms is transmitted to the valve stems to open and close the engine valves. The lubricating oil supplying structure for the valve apparatus includes an oil passage provided in the cylinder head along an axial direction of the camshafts and formed from a single passage at a position lower than the rocker arm shafts between the intake and exhaust valves. A pair of oil injection oil paths is formed so as to be directed independently for the individual rocker arms from the oil passage.
According to an embodiment of the present invention, valve stem pressing portions are formed at locations at which the rocker arms contact with the valve stems side in a continuous relationship to lower faces of the rocking arms of the rocker arms. The direction in which the oil injection oil paths are directed to the rocker arms is directed toward the lower faces of the rocking arms.
According to an embodiment of the present invention, the lower face of the rocker arm is formed wherein a curved recessed portion is the lowest portion toward the valve stem pressing portion.
According to an embodiment of the present invention, clearance adjustment members for adjusting gaps between the valve stem axial ends and the rocker arms are formed exchangeably as separate members between the valve stems and the valve stem pressing portions of the rocker arms.
According to an embodiment of the present invention, the oil passage is provided in a protuberance protruding from a lower face of a connecting bottom wall which interconnects lower portions of a pair of support walls which are provided on the cylinder head and support the opposite axial ends of the rocker arm shaft.
According to an embodiment of the present invention, the camshafts are configured independently as an intake camshaft and an exhaust camshaft and disposed at a position above the rocker arms, and sliding portions between the rocker arms and the cam faces are provided on upper faces of the rocker arms.
According to an embodiment of the present invention, the rocker arm shafts are disposed between the intake and exhaust camshafts such that the sliding portions of the rocker arms are disposed so as to be directed outwardly relative to each other. The rocker arm shafts are disposed at heightwise positions different from each other with reference to an extension line of the cylinder center axis. The oil passage is disposed in an offset relationship to the rocker arm shaft disposed at the higher position.
According to an embodiment of the present invention, a cylinder of the internal combustion engine is mounted in an inclined relationship with respect to the vertical direction such that, in a state in which the internal combustion engine is mounted on a vehicle. A tip end of the rocker arm disposed on one of the two rocker arm shafts, which is disposed at the higher position, is directed obliquely upwardly while a tip end of the rocker arm disposed on the other one of the two rocker arm shafts, which is disposed at the lower position, is directed obliquely downwardly. The oil injection oil path is formed such that the injection direction from the oil injection oil path to the valve stem pressing portion of that one of the rocker arms in which the oil passage is disposed in an offset relationship is directed to the tip end of the rocker arm. The oil injection oil path is formed such that the injection direction from the oil injection oil path to the valve stem pressing portion of the other rocker arm is directed to the pivotally supporting base portion of the rocker arm.
According to an embodiment of the present invention, the oil passage is formed from the single passage extending along the camshafts at a position lower than the rocker arm shafts between the intake and exhaust valves, and the paired oil injection oil paths are provided so as to be directed independently of the individual rocker arms from the oil passage. Therefore, while the path for the injection oil is reduced in length, oil is supplied from the single oil passage directly to the rocker arms, and oil to be supplied to the oil injection oil paths is supplied from the common oil passage. Consequently, it is possible to facilitate assurance of the amount of oil. Further, since the oil injection oil paths are provided from the single oil passage, space saving of the lubricating oil supplying structure can be anticipated. Thus, the fabrication cost can be reduced.
According to an embodiment of the present invention, the lower faces of the rocking arms of the rocker arms are formed in a continuous relationship to the valve stem pressing portions. Thus, the direction in which the oil injection oil paths are directed to the rocker arms is directed toward the lower faces of the rocking arms. Therefore, even if part of the injected oil does not directly reach the valve stem pressing portions, it flows along the lower faces of the rocking arms and is supplied to the valve stem pressing portions. Consequently, the oil supplying amount to the valve stem pressing portions can be increased.
According to an embodiment of the present invention, the lower face of the rocker arm is formed as a curved recessed portion which is the lowest portion toward the valve stem pressing portion. Therefore, oil sticking to the lower face can positively flow to the sliding portion side between the valve stem pressing portion and the valve stem axial end to collect the oil.
According to an embodiment of the present invention, the clearance adjustment members are formed as separate members between the valve stem pressing portions of the rocker arms and the valve stem axial ends. Therefore, the necessity for such a screw adjustment mechanism disposed at a tip end of a rocker arm as in a conventional technology is eliminated. Further, since the sliding faces of the valve stem pressing portions are configured from curved faces, it becomes possible to supply oil flowing along the lower faces of the rocker arms with certainty to the sliding faces of the valve stem pressing portions.
According to an embodiment of the present invention, the oil passage is provided in the connecting bottom wall of the paired support walls which support the opposite axial ends of the rocker arm shaft and this is provided in the protuberance protruding from the lower face. Therefore, the oil passage can be provided in the cylinder head. Thus, an increase in the size of the cylinder head in the heightwise direction can be suppressed.
According to an embodiment of the present invention, the sliding portions are provided on the upper faces of the rocker arms. Therefore, the injected oil can be supplied to the valve stem side end portions without being obstructed by cam lobes of the camshafts.
According to an embodiment of the present invention, where the intake and exhaust rocker arm shafts are disposed closely to each other, they are disposed differently from each other in the cylinder axial direction, and the oil passage is disposed in an offset relationship to the rocker arm shaft side disposed at the higher position. Therefore, the free space can be utilized effectively to compactly dispose the oil passage.
According to an embodiment of the present invention, the internal combustion engine is mounted on the vehicle such that the tip ends of the two rocker arms are directed obliquely upwardly and obliquely downwardly, and the oil injection oil path to the rocker arm disposed at the higher position is formed so as to be directed to the tip end of the rocker arm while the oil injection oil path to the rocker arm disposed at the lower position is formed so as to be directed to the pivotally supporting base portion of the rocker arm shaft. Therefore, even where it is difficult to direct an oil injection oil path directly to the tip end of the rocker arm, it is possible to allow oil to flow and be supplied to the tip end of the rocker arm from the pivotally supporting base portion of the rocker arm. Consequently, while a reduction of the length of the oil injection oil path is achieved, oil supply can be carried out with certainty.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.